There is not such thing as someone or a company offering a service for free. All have to make a living, so even if it is offered as free, there is always a catch.

What I would advise you to do is to search the net for softwares to create cards, invitations, etc… such as tucows.com and download a trial program. This will allow you to create your invitations before the trial expires (usually a month)

I made my own invitations on my home computer. You can buy reams of nice paper, and try heaps of different fancy fonts. They looked really really good.

I had my invitations on Gold Paper and normal white paper on the inside and glued on a strip of bronze ribbon.

I also made my Order of Service. and I also made cards for the Tables at the reception which I had incluced the Menu of the meal, Time of everything that was happening, etc etc etc (I also had on the back a lil pic of me and my husband)

OR you can always set up a wedding website, and put ALL the info onto that! Once it is set up, then you can email everyone that your sis wants to invite along with the website address and ask them to RSVP on it. And it is totally free.

There are so many firms, which can offer you free printing but they always adjust charges in shipping or card price. Or may be those firms can give this facility on selected wedding invitations.

I suppose you should try to contact http://www.personalinvitationcards.com. There you can get many cheap wedding cards, and if you offer them high volume then may be that firm agree to give you free printing.